1. Technical Field
This application relates to the field of network communication, and more specifically to initiating a communication session between participants in separate networks that implement dissimilar session initiation protocols.
2. Background Information
A session initiation protocol (SIP) is a signaling protocol used to initiate a communication session between two (or more) participants within an Internet protocol (IP) network, such as a messaging network. The communication session may be a telephone call over the Internet, an instant messaging (IM) session, a multi-media conference session, or other type of communication activity between participants. The participants (initiator and invitee) may interface to the network by way of an application running on a computer, such as an IM client application, or a device, such as an IP phone, as examples. Throughout the specification, unless indicated otherwise, the terms “initiator” and “invitee” refer to a client application, device, or other network communication endpoint, and not the participants themselves. The term “endpoint” refers to one or more interfaces such as a client application, IP phone, or any program (software endpoint), set of programs, device (hardware endpoint), or set of devices that enable participants to communicate with one another within or between network(s).
During the initiation (also referred to as “signaling”) phase of a communication session, SIP messaging first occurs between the initiator and a SIP server associated with the initiator's network. To initiate the communication session, the initiator sends a SIP invitation message to the SIP server. The SIP invitation message typically includes the invitee's address as well as a session description. For example, a session description may indicate that the prospective session is a Voice over Internet Protocol (VoIP) telephone session, a video conference session, or other type of media session. The SIP server then communicates the SIP invitation message to the invitee. The SIP invitation message is followed by further SIP messaging between the initiator and the invitee via the SIP server. The SIP messaging provides information that is used to prepare the initiator and the invitee for the communication session.
SIP messaging may also ascertain whether the invitee's address (e.g., IP address) is correct and whether the invitee is available. SIP messaging may indicate that certain of the invitee's computer and/or network resources are required for the communication session and should be reserved if the communication session is going to occur. For example, a video application may need to be accessible and executable at the invitee's computer if SIP messaging indicates that the communication session is a video conference session. In addition, SIP messaging may indicate that computer and/or network resources, such as memory, will have to be allocated to the session to ensure a cohesive communication exchange. If the invitee can satisfy the communication requirements, a SIP message indicating so is sent by the invitee to the SIP server. The SIP server notifies the initiator accordingly. After a session has been initiated, the endpoints exchange data by way of data oriented protocol, such as the IP, without further invoking the SIP or the SIP server unless the session settings are modified or until the session is terminated by the initiator or invitee.
There are different SIP standards. For example, the Internet Engineering Task Force (IETF) has designated RFC 3261 as a SIP standard. RFC 3261 is widely used as a signaling protocol for VoIP and has been evolving and expanding as technologies advance. Other SIP standards exist, such as those that are customized for SIP servers that support specific network domains. For example, Microsoft® utilizes a customized SIP to support the popular Microsoft® Office Communicator (MOC) client. A substantial problem arises because MOC SIP fields are different from the RFC 3261 SIP fields. Thus, a MOC SIP message is not discernable in the RFC 3261 domain, and a RFC 3261 SIP message is not discernable in the MOC domain. Therefore, a communication session cannot be established between a participant in the MOC domain and a participant in the RFC 3261 domain.
There presently exists a need to initiate a communication session between an initiator and an invitee in separate networks that implement dissimilar session initiation protocols. A SIP adaptor solves the technical problem of communicating session information between endpoints in networks that use dissimilar SIP standards.